Impact cylinder apparatus

ABSTRACT

An impulse stamping device having a cylinder in which a hollow piston and piston rod are mounted. The piston rod extends outwardly of the cylinder and has mounted at its end a dieholder. A ram having a head at its upper end is mounted within the hollow rod. The head is adapted to seat within a second cylinder located axially at the upper end of the first cylinder. Compressed gas is fed selectively to the cylinders to operate the piston rod and ram in sequence to first lower the dieholder and thereafter ram the die against the workpiece.

United States Patent IMPACT CYLINDER APPARATUS 5 Claims, 5 Drawing Figs.

US. Cl 173/114,

173/1 34,227/147 Int. Cl B2511 9/00 Field of Search 173/1 12,

Primary Examiner-James A. Leppink Attorney-Kurt Kelman ABSTRACT: Animpulse stamping device having a cylinder in which a hollow piston andpiston rod are mounted. The piston rod extends outwardly of the cylinderand has mounted at its end a dieholder. A ram having a head at its upperend is mounted within the hollow rod The head is adapted to seat withina second cylinder located axially at the upper end of the firstcylinder. Compressed gas is fed selectively to the cylinders to operatethe piston rod and ram in sequence to first lower the dieholder andthereafter ram the die against the workpiece.

PATENTEDSEP28I971 SHEET 1 [1F 2 Fig.7

AGEUT sum for 2 PATENTED'SEHB isn INVENTOR SABMlo MArsvsAuA MENF IMPACTCYLINDER APPARATUS BACKGROUND OF THE INVENTION The present inventionrelates to an impact stamping device and in particular to an improveddevice by which the die is first moved into position against theworkpiece and is the rammed.

Generally speaking, the operation of stamping and rivet fasteningapparatus by employing an impact impulse is most desirable, because theapplication of an impact force permits these apparatuses to bedimensioned smaller and lighter than those which work by the applicationof static stress and pressure.

However, when conventional impact cylinder apparatus for example, amarking machine, is employed, the impact piston jumps up due to thereaction of the impact of the die against the workpieces. This oftenresults in two or more successive impulses, so that the article isdisplaced by the impact vibration and may often have duplicate stamppositions effected from the same letter or figure. Many of otherconventional examples presented different defects such as the generationof back pressure on the piston during operation, thus decreasing thework efficiency.

It is the object of the invention to provide an improved apparatus, ofsimple structure and function overcoming the defects of the conventionaldevices and providing improved finished workpieces at high efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section of theapparatus of the invention, in

' the initial state of operation,

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings the apparatusof the present invention comprises, a cylinder 1 which has an upper head2 and a lower head 3. A hollow piston 4 slides hermetically insidecylinder 1 and is integral with a hollow piston rod 5. A piston 7 isformed on the upper part of a ram 6 sliding hermetically inside bothhollow piston 4 and hollow piston rod 5. A stamp holder 9 holding astamp die 8 is slidably supported by the lower part of hollow piston rod5. Hollow piston 4, lower head 3, hollow piston rod and piston 7 arerespectively provided with respectively a packing 10, a gland packingl1, and packings l2 and 13. The upper head is internally cutout to forman air cavity 14 and a cylinder portion 15 above it. The piston 7hermetically sealed with packing 13 slides inside the cylindricalportion 15. Orifices 16 are distributed in the periphery near at thebottom of hollow piston rod 5. An annular opening 17 is positioned inthe bottom of hollow piston rod 5 and supports an upper portion 24 ofthe stamp holder 9. A lower portion 18 of stamp holder 9 has a hole 20for holding a tool or die 8 by a Shank 19 which is inserted in theholder and supported by a set screw or bolt. The space within cylinder 1surrounding the piston rod 5 under hollow piston 4 is defined a and thespace within cylinder 1 between upper head 2 and hollow piston 4 isdefined b.

Numerals 21 and 22 denote respectively four-way and three-way changeovervalves, 23 a gaseous pressure source, 25, 26 and 27 gas ports for bothinlet and outlet, 29 a velocity control valve, and 30 an article to bestamped, which is placed on a table 31.

The functions of stamping operation for the examples of FIGS. 1-3 willbe explained.

In FIG. I, compressed gas is initially introduced to a space a insidecylinder 1 through port 27 applying a pressure on the bottom surface Sof hollow piston 4, causing the hollow piston 4 to be pushed up intocontact with the upper head 2 assuming the upper dead point piston 7 andram 6 are carried by hollow piston 4 and supported with the pistonsealed within the cylinder 15, whose orifice 26 is open to atmosphere.

When four-way valve 21 is changed over, compressed gas in said space aunder hollow piston 4 is discharged through port 27 and new compressedgas through port 25 from the gaseous pressure source 23 is introducedinto air cavity 14, and then hollow piston 4 starts descending as shownin FIG. 2. With regard to piston 7 and ram 6 which are movably supportedrelative to hollow piston 4; since cylindrical portion 15 is opened tothe atmosphere through three-way changeover valve 22, a force F,generated by compressed gas introduced into air cavity l4 acts on piston7 in an upward manner to support it at the upward end in the cylinder 15as shown in FIG. 2. Therefore F 1 may be calculated as follows:

A cross section of piston 7 A cross section of ram 6 P, gas pressureinside air cavity 14 W: weight sum of ram 6 and piston 7 As the hollowpiston 4 continues descending from the position of FIG. 2, the stamp 8comes to contact with article 30 until the bottom face 37 of the hollowpiston rod 5 presses against the upper surface 38 of the lower portion18 of stamp holder 9 and impresses stamp 8 on article 30.

The three-way valve 22 is then changed over, and compressed gas issupplied through port 26 against the face of the piston 7 so that piston7 and ram 6 themselves start descending. As piston 7 descends downwardand passes out of cylindrical portion 15 reaching the air cavity 14,compressed gas introduced into the air cavity b formed above the hollowpiston 4 by the descent of hollow piston 4 inside cylinder Isimultaneously comes to act on piston 7 and ram 6 causing ram 6 toaccelerate rapidly in the downward motion.

In this condition, as the diameter of hollow piston 4 is much largerthan the diameter of ram 6, the air cavity b serves as a gas reservoir.Even if the quantity of compressed gas supplied to the air cavity bthrough ports 25 and 26 is rather little, pres sure in the air cavity bdoes not substantially change and maintains a sufficiently high pressureduring the high accelerative motion of ram 6.

If the downward force on ram 6 is denoted by F then F =A P -W wherein, Pdenotes the pressure inside the air cavity b on hollow piston 4 as shownin FIG. 3.

In this manner ram 6 being gradually accelerated by force F collidesagainst the upper surface of stamp holder 9 as shown in FIG. 3. If theenergy obtained in case of the collision is denoted by E, then E=F '-lwherein, [denotes the length of descent of ram 6 to its point ofcollision against stamp holder 9,

F '=A P '+W wherein, P denotes the mean pressure in the air cavity bduring the descent of ram 6.

As a result of the colliding of ram 6 against stamp holder 9, article 30is marked by stamp die 8, therefore, one cycle of stamping operation inthe present invention is finished.

If changeover valves 21 and 22 are returned to the state of FIG. 1,hollow piston 4 is pushed upward, and accordingly ram 6 is also liftedto restore the state of FIG. 1.

All the above descriptions concern a stamping operation rivet fasteningemploying the same apparatus is described with reference to FIGS. 4 and5. In these drawings, a punch 32 for fastening rivets is suspended fromthe lower part of hollow piston rod 5. In FIG. 5, 33 denotes an anvilplaced on the table of a press frame, 34 a rivet, 35 and 36 articles tobe incorporated by the rivet.

When four-way valve 21 is changed over similarly to the case of stampingoperation, hollow piston 4 and hollow piston rod 5 descend, and sobottom face 37 of hollow piston rod 5 pushes the articles against anvil33 as shown in FIG. 5. At the same time punch 32 contacts with the rivetand is pushed upward.

Subsequently, when three-way valve 22 is changed over and ram 6 descendsrapidly then the bottom end of ram 6 strikes the upper end of punch 32to fasten rivet 34.

In the stamping operation, the present invention provides a preliminarypressing operation which can assure a clear finished workpiece withoutthe least displacement between the stamp and articles, even if the ramshould rebound and stamp repeatedly. Similar advantage will also beapparent in the rivet fastening operation. Rivet fastening is performedby the impact force of the ram only after pressing and contacting thedie and articles together. Thus rivet fastening operation is performedexcellently. Even if a rivet is inserted askew or on the tilt or in arivet hole of surplus size, it will be corrected to its normal positionby the preliminary contact and the part to be combined will be perfectlyfastened. Furthermore, apparatus of smaller dimension will render largeeffective power so that oversized apparatus is not required.

As illustrated above, the present invention permits the hollow piston 4and the hollow piston rod 5 to serve as a pressing mechanism in thestamping and the rivet fastening operation, and to lift piston 7 and ram6 so that piston 7 may be inserted into cylindrical portion andsupported. Hollow piston 4 is caused to descend downward by compressedgas introduced in air cavity 14 through port 25, and at the same timepiston 7 and ram 6 are caused to be pushed upward and supported atupward end of cylindrical portion 15 by said compressed gas. After that,by operating changeover valve 22, compressed gas is supplied throughport 26 to piston 7, causing piston 7 and ram 6 to descend downward. Thecompressed gas in the air cavities l4 and b cylinder 1 cause ram 6 toaccelerate rapidly downward. As the air cavity inside cylinder 1 has alarger volume of sufiiciently, compressed gas the air cavities aremaintained at a sufficiently high pressure during the acceleratingmotion of ram 6. The downward motion of ram 6 is not prevented by anyback pressure because the piston rod 5 is opened to the atmospherethrough orifices 16. Consequently the present invention providesapparatus of high efficiency capable of reduced manufacturing cost.

What is claimed is:

1. Impact apparatus comprising a cylinder having an upper and lower headdefining therebetween a first air cavity, said upper head having acutout portion defining a second air cavity, an axially hollow pistonand integral piston rod, said hollow piston movably mounted within saidfirst air cavity and dividing said cavity into upper and lower portions,said hollow piston rod extending through said lower head outwardly ofsaid cylinder and having an opening at the end thereof, a die holdermovably mounted in the opening of said hollow piston rod, a ramslidingly mounted within said hollow piston and piston rod, said ramextending between said die holder and the upper end of said hollowpiston, a ram piston head integral with the upper end of said ram havinga profile adapted for insertion into said second cavity, means forintroducing a gas under pressure into said upper portion of said firstcavity to act simultaneously on said hollow piston and said ram pistonhead, and means for introducing a gas under pressure to said secondcavity to act on said ram piston head whereby said hollow piston and rodmay be moved downwardly through said first cavity at a predeterminedrate and said ram may be moved downwardly through said hollow piston rodat a second predetermined rate.

2. The apparatus according to claim 1 including means for acceleratingsaid ram a speed greater than said piston rod.

3. The apparatus according to claim 1 wherein the ram piston head has alower surface adapted to be carried by said hollow piston and whereinmeans are provided for introducing gas under pressure into the lowerportion off said first cavity to lift said hollow piston and said rampiston head.

4. The apparatus according to claim 3 wherein each of said means forintroducing air comprises selectively o erable valve means and means foroperating said valves to o tam sequential movement of said piston rodand ram.

5. The apparatus according to claim 1 wherein said second air cavitycomprises a cylinder adapted to receive said ram piston head in sealingengagement therewith, said ram piston head being adapted to move out ofsuch engagement on introduction of gas under pressure to said secondcavity and into said first cavity to be acted thereon by theintroduction of gas under pressure thereto.

1. Impact apparatus comprising a cylinder having an upper and lower headdefining therebetween a first air cavity, said upper head having acutout portion defining a second air cavity, an axially hollow pistonand integral piston rod, said hollow piston movably mounted within saidfirst air cavity and dividing said cavity into upper and lower portions,said hollow piston rod extending tHrough said lower head outwardly ofsaid cylinder and having an opening at the end thereof, a die holdermovably mounted in the opening of said hollow piston rod, a ramslidingly mounted within said hollow piston and piston rod, said ramextending between said die holder and the upper end of said hollowpiston, a ram piston head integral with the upper end of said ram havinga profile adapted for insertion into said second cavity, means forintroducing a gas under pressure into said upper portion of said firstcavity to act simultaneously on said hollow piston and said ram pistonhead, and means for introducing a gas under pressure to said secondcavity to act on said ram piston head whereby said hollow piston and rodmay be moved downwardly through said first cavity at a predeterminedrate and said ram may be moved downwardly through said hollow piston rodat a second predetermined rate.
 2. The apparatus according to claim 1including means for accelerating said ram a speed greater than saidpiston rod.
 3. The apparatus according to claim 1 wherein the ram pistonhead has a lower surface adapted to be carried by said hollow piston andwherein means are provided for introducing gas under pressure into thelower portion of said first cavity to lift said hollow piston and saidram piston head.
 4. The apparatus according to claim 3 wherein each ofsaid means for introducing air comprises selectively operable valvemeans and means for operating said valves to obtain sequential movementof said piston rod and ram.
 5. The apparatus according to claim 1wherein said second air cavity comprises a cylinder adapted to receivesaid ram piston head in sealing engagement therewith, said ram pistonhead being adapted to move out of such engagement on introduction of gasunder pressure to said second cavity and into said first cavity to beacted thereon by the introduction of gas under pressure thereto.